1. Field of the Invention
The present invention relates to an IPv6/IPv4 translator, and more precisely, to automatic address generation.
2. Description of the Related Art
A description on header part translation between IPv6 and IPv4 protocols is found in paragraph 0049 of Patent Document 1.
However, Patent Document 1 describes a packet processor, a packet processing method and a packet exchanger, aiming at implementing memory saving as well as realizing smooth pipeline processing in which there is no competition in accessing a shared memory between processing in different layers.
Contrary to the above, the present invention allows automatic address generation without changing address settings for a Domain Name System (hereafter abbreviated as DNS) server and thus its objective is different from that of Patent Document 1.
[Patent Document 1]
Japanese Laid-open Patent Application No. 2000-115234 The method which an IPv6/IPv4 translator uses in order to provide the user with a user-friendly environment is the technique whereby a DNS server translates addresses as a method for dynamically generating addresses. Concretely, this is achieved by sending a query packet in a DNS to specific equipment having a DNS proxy function from a client. This means that an automatic address generation service is provided for a specified client.
In general, to send a DNS query to a specific DNS proxy, it is necessary for a client to set up the address as a DNS server to the relevant DNS proxy.
However, since this setup change cannot be expected for an unspecified client, a structure, in which an IPv6/IPv4 translator can be utilized without implementing such a setup change, becomes necessary.
The present invention provides a structure in which an IPv6/IPv4 translator can be used without necessitating the client to change the setup for a DNS server.
FIG. 1 is a block diagram in the case where a client utilizes the DNS proxy function of a translator as the DNS server. In FIG. 1, it is necessary to specify the DNS proxy in translator 2 as the DNS server for client 1 to utilize automatic address generation by DNS. The DNS proxy in translator 2 returns an appropriate address, determined by the types of the address obtained and types of the address queried and setup contents, to client 1.
FIG. 2 is an illustrative drawing of the operation when a client queries an IPv6 address and shows an example in which the IPv6 address is automatically generated.
(1) Client 1 requests DNS proxy 2 to reply the IPv6 address for “www.oxΔ.com” (“AAAA” record).
(2) DNS proxy 2 forwards the request from client 1 to DNS server 3.
(3) DNS server 3 queries the IPv6 address corresponding to “www.oxΔ.com” to other name servers not shown in the drawing. However, DNS server 3 obtains the response that no corresponding IPv6 address is present. (If the corresponding IPv6 address is present at that time, DNS proxy 2 returns the received IPv6 address to client 1.)
(4) DNS proxy 2 requests DNS server 3 to reply the IPv4 address (“A” record) corresponding to “www.oxΔ.com”.
(5) DNS server 3 queries the IPv4 address corresponding to “www.oxΔ.com” to other name servers not shown in the drawing and obtains the corresponding IPv4 address and notifies DNS proxy 2 of that address.
(6) DNS proxy 2 generates an address using a Dummy Prefix prepared for mapping the IPv4 address to an IPv6 address and returns it to client 1 as an IPv6 address.
FIG. 3 is an illustrative drawing showing the operation when a client queries an IPv4 address and shows an example in which an IPv4 address is automatically generated.
(1) Client 1 requests DNS proxy 2 to reply the IPv4 address for “www.oxΔ.com” (“A” record).
(2) DNS proxy 2 forwards the request from client 1 to DNS server 3.
(3) DNS server 3 queries the IPv4 address corresponding to “www.oxΔ.com” to other name servers not shown in the drawing. However, DNS server 3 obtains the response that no corresponding IPv4 address is present. (If the corresponding IPv4 address is present at that time, DNS proxy 2 returns the received IPv4 address to client 1.)
(4) DNS proxy 2 requests DNS server 3 to reply the IPv6 address (“AAAA” record) corresponding to “www.oxΔ.com”.
(5) DNS server 3 queries the IPv6 address corresponding to “www.oxΔ.com” to other name servers not shown in the drawing and obtains the corresponding IPv6 address and notifies DNS proxy 2 of that address.
(6) DNS proxy 2 allocates the IPv4 address prepared for mapping the IPv6 address to the IPv4 address to this IPv6 address and returns it to client 1 as an IPv4 address.
There is absolutely no problem with these conventional usages as long as the environment is such that a client can specify the DNS proxy of a translator as a DNS server. However, such a setup change cannot be expected when services are provided for unspecified general clients.